Method of Manufacturing Solid-State Battery

This application is based on and claims the benefit of priority from Japanese Patent Application No. 2024-058322, filed on 30 Mar. 2024, the content of which is incorporated herein by reference.

The present invention relates to a method of manufacturing a solid-state battery.

In recent years, research and development has been conducted on solid-state batteries that contribute to energy efficiency in order to ensure that more people have access to affordable, reliable, sustainable, and advanced energy.

As a solid-state battery, an all-solid-state battery is known, in which a solid-state electrolyte layer is arranged between a positive electrode and a negative electrode.

Japanese Unexamined Patent Application, Publication No. 2017-10816 describes a method of manufacturing an all-solid-state battery in which a positive electrode laminate, an intermediate solid-state electrolyte layer, and a negative electrode laminate are laminated in this order. Here, the positive electrode laminate has a positive electrode charge collector layer, a positive electrode active material layer, and a first solid-state electrolyte layer in this order, and the negative electrode laminate has a second solid-state electrolyte layer, a negative electrode active material layer, and a negative electrode charge collector layer containing copper, in this order. The method of manufacturing the all-solid-state battery includes a first pressing step of pressing the positive electrode laminate, a second pressing step of pressing the negative electrode laminate, and a third pressing step of pressing the positive electrode laminate, the intermediate solid-state electrolyte layer, and the negative electrode laminate. In this case, the pressing pressure of the first pressing step is higher than the pressing pressure of the third pressing step, and the pressing temperature of the first pressing step is greater than or equal to 150° C. and less than or equal to 175° C. The pressing pressure of the second pressing step is higher than the pressing pressure of the third pressing step, and the pressing temperature of the second pressing step is less than or equal to 125° C. Furthermore, the pressing temperature of the third pressing step is less than or equal to 125° C., and before being pressed in the third pressing process, the intermediate solid-state electrolyte layer is not pressed at a pressure exceeding the pressing pressure of the third pressing step.

Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2017-10816

However, in the method of manufacturing the all-solid-state battery described in Japanese Unexamined Patent Application, Publication No. 2017-10816, if the pressing pressure of the first pressing step and the pressing pressure of the second pressing step are high, the first solid-state electrolyte layer and the second solid-state electrolyte layer become dense and cracks occur in the electrodes during pressing in the third pressing step. On the contrary, if the pressing pressure of the first pressing step and the pressing pressure of the second pressing step are low, the first solid-state electrolyte layer and the second solid-state electrolyte layer do not become dense and the resistance of the all-solid-state battery increases.

An object of the present invention is to provide a method of manufacturing a solid-state battery that is able to lower the resistance of the solid-state battery and suppress the occurrence of cracks in the electrodes.

The present invention can provide a method of manufacturing a solid-state battery that is able to lower the resistance of the solid-state battery and suppress the occurrence of cracks in electrodes.

An embodiment of the present invention will be described below with reference to the accompanying drawings.

shows a solid-state battery according to one embodiment of the present invention.

The solid-state batteryincludes an electrode laminate in which a negative electrode, an intermediate layer, an electrolyte layer, a positive electrode, an electrolyte layer, an intermediate layer, and a negative electrodeare laminated sequentially. Here, the electrolyte layerhas a first solid-state electrolyte layer, a gel electrolyte layer, and a second solid-state electrolyte layerlaminated sequentially in the laminating direction of the electrode laminate. At this time, a portion of the gel electrolyte included in the gel electrolyte layermay permeate the first solid-state electrolyte layerand/or the second solid-state electrolyte layer.

In the negative electrode, a negative electrode composite layerand a negative electrode charge collectorare laminated sequentially in the laminating direction of the electrode laminate. Here, a negative electrode charge collector tabextends from one end of the negative electrode charge collector.

The positive electrodehas a positive electrode composite layer, a positive electrode charge collector, and a positive electrode composite layerlaminated sequentially in the laminating direction of the electrode laminate. When the positive electrodeis viewed from above with respect to the laminating direction of the electrode laminate, the outer circumference of the positive electrode composite layeris inside the outer circumference of the positive electrode charge collector, and an insulating frameis provided at the outer circumference of the positive electrode composite layer. When the insulating frameis viewed from above with respect to the laminating direction of the electrode laminate, the outer circumference of the insulating frameis at approximately the same position as the outer circumference of the positive electrode charge collector. Here, a positive electrode charge collector tabextends from the end of the positive electrode charge collectoropposite to the end from which the negative electrode charge collector tabextends.

Note that the solid-state batterymay be any battery that has an electrode laminate in which a negative electrode, an intermediate layer, an electrolyte layer, and a positive electrodeare laminated sequentially. For example, the solid-state batterymay have multiple positive electrodes. Alternatively, the solid-state batterymay have a single negative electrode, a single intermediate layer, and a single electrolyte layer. In this case, the positive electrodehas a positive electrode composite layerand a positive electrode charge collector, which are laminated sequentially in the laminating direction of the electrode laminate. Further, the solid-state batterydoes not necessarily include the intermediate layer.

Next, a method of manufacturing a solid-state batterywill be explained with reference to.

A laminate Lof an intermediate layer-a negative electrode laminate is prepared by pressing a material that constitutes an intermediate layeron the surface of the negative electrodeon which the negative electrode composite layeris disposed (step 1A; see). The method of disposing the material that constitutes the intermediate layeron the surface of the negative electrodeon which the negative electrode composite layeris disposed may be, but is not limited to, a method in which the intermediate layeris transferred onto the negative electrode composite layer, with an intermediate layer transfer sheet. The intermediate layer transfer sheet is prepared, for example, by coating a support sheet with a slurry obtained by dispersing the material that constitutes the intermediate layerin a solvent and then drying the slurry. The pressing pressure in the step 1A may be, but is not limited to, greater than or equal to 400 MPa and less than or equal to 1000 MPa. The pressing temperature in the step 1A may be, but is not limited to, greater than or equal to 25° C. and less than or equal to 150° C.

A first solid-state electrolyte layer-intermediate layer-negative electrode laminate Lis prepared by pressing the material that constitutes the first solid-state electrolyte layerwith the material being disposed on the surface of the intermediate layer-negative electrode laminate Lwhere the intermediate layeris disposed (step 2A; see). The method of disposing the material that constitutes the first solid-state electrolyte layeron the surface of the intermediate layer-negative electrode laminate Lon which the intermediate layeris disposed may be, but is not limited to, a method in which the first solid-state electrolyte layeris transferred onto the intermediate layer, with a first solid-state electrolyte layer transfer sheet. The first solid-state electrolyte layer transfer sheet is prepared, for example, by coating a support sheet with a slurry obtained by dispersing a solid-state electrolyte, which has a median diameter of less than or equal to 1 μm, in a solvent and then drying the slurry. At this time, the pressing pressure in the step 2A is preferably higher than the pressing pressure in the step 4A described below. This densifies the first solid-state electrolyte layerand suppresses damage and deformation of each layer. The pressing pressure in the step 2A may be any pressure that can densify the first solid-state electrolyte layer, for example, greater than or equal to 600 MPa and less than or equal to 1000 MPa. The pressing temperature in the step 2A may be, but is not limited to, greater than or equal to 25° C. and less than or equal to 150° C.

The density of the first solid-state electrolyte layermay be, but is not limited to, greater than or equal to 1.65 g/cmand less than or equal to 2.00 g/cm. The porosity of the first solid-state electrolyte layermay be, but is not limited to, greater than or equal toand less than or equal to 7%. The thickness of the first solid-state electrolyte layermay be, but is not limited to, greater than or equal to 1 μm and less than or equal to 7 μm.

A second solid-state electrolyte layer-positive electrode laminate Lis prepared by pressing the material that constitutes the second solid-state electrolyte layerwith the material being disposed on both surfaces of a positive electrodewhere the positive electrode composite layerand the insulating frameare disposed (step 3; see). The method of disposing the material that constitutes the second solid-state electrolyte layeron both surfaces of the positive electrodewhere the positive electrode composite layerand the insulating frameare disposed may be, but is not limited to, a method in which the second solid-state electrolyte layeris transferred onto the positive electrode composite layerand the insulating frame, with a second solid-state electrolyte layer transfer sheet. The second solid-state electrolyte layer transfer sheet is prepared, for example, by coating a support sheet with a slurry obtained by dispersing a solid-state electrolyte, which has a median diameter of less than or equal to 1 μm, in a solvent and then drying the slurry. The pressing pressure in the step 3 is preferably higher than the pressing pressure in the step 4A described below. This densifies the second solid-state electrolyte layerand suppresses damage and deformation of each layer. The pressing pressure in the step 3 may be any pressure that can densify the second solid-state electrolyte layer, for example, greater than or equal to 800 MPa and less than or equal to 1200 MPa. The pressing temperature in the step 3 may be, but is not limited to, greater than or equal to 25° C. and less than or equal to 1000° C.

The density of the second solid-state electrolyte layermay be, but is not limited to, greater than or equal to 1.65 g/cmand less than or equal to 2.00 g/cm. The porosity of the second solid-state electrolyte layermay be, but is not limited to, greater than or equal to 1% and less than or equal to 7%. The thickness of the second solid-state electrolyte layermay be, but is not limited to, greater than or equal to 1 μm and less than or equal to 7 μm.

An electrode laminate is prepared by pressing the material that constitutes the gel electrolyte layerwith the material being disposed between the surface of the first solid-state electrolyte layer-intermediate layer-negative electrode laminate Lwhere the first solid-state electrolyte layeris disposed and the surface of the second solid-state electrolyte layer-positive electrode laminate Lwhere the second solid-state electrolyte layeris disposed (step 4A; see). Consequently, even if the first solid-state electrolyte layerand the second solid-state electrolyte layerare densified, cracking of the negative electrodeand/or positive electrodeduring pressing is suppressed. The method of disposing the material that constitutes the gel electrolyte layermay be, but is not limited to, a method in which the gel electrolyte layeris transferred onto the first solid-state electrolyte layeror second solid-state electrolyte layer, with a gel electrolyte layer transfer sheet. The gel electrolyte layer transfer sheet is prepared, for example, by coating a support sheet with a slurry obtained by dispersing the material that constitutes the gel electrolyte layerin a solvent and then drying the slurry. The pressing pressure in the step 4A may be any pressure that can integrate the electrolyte layer, for example, less than or equal to 500 MPa.

The machine used to manufacture the solid-state batterymay be, but is not limited to, a roll press machine or flat plate press machine.

A method of manufacturing the solid-state batterywithout the intermediate layerwill now be described with reference to.

A first solid-state electrolyte layer-negative electrode laminate LA is prepared by pressing the material that constitutes the first solid-state electrolyte layerwith the material being disposed on the surface of the negative electrodewhere the negative electrode composite layeris disposed (step 2B; see). The method of disposing the material that constitutes the first solid-state electrolyte layeron the surface of the negative electrodewhere the negative electrode composite layeris disposed may be, but is not limited to, a method in which the first solid-state electrolyte layeris transferred onto the negative electrode composite layer, with a first solid-state electrolyte layer transfer sheet. The first solid-state electrolyte layer transfer sheet is prepared, for example, by coating a support sheet with a slurry obtained by dispersing a solid-state electrolyte, which has a median diameter of less than or equal to 1 μm, in a solvent and then drying the slurry. The pressing pressure may be any pressure that can densify the first solid-state electrolyte layer.

The second solid-state electrolyte layer-positive electrode laminate Lis prepared by the method described above (step 3; see).

An electrode laminate is prepared by pressing the material that constitutes the gel electrolyte layerwith the material being disposed between the surface of the first solid-state electrolyte layer-negative electrode laminate LA where the first solid-state electrolyte layeris disposed and the surface of the second solid-state electrolyte layer-positive electrode laminate Lwhere the second solid-state electrolyte layeris disposed (step 4B; see). Consequently, even if the first solid-state electrolyte layerand the second solid-state electrolyte layerare densified, cracking of the negative electrodeand/or positive electrodeduring pressing is suppressed. The method of disposing the material that constitutes the gel electrolyte layermay be, but is not limited to, a method in which the gel electrolyte layeris transferred onto the first solid-state electrolyte layeror the second solid-state electrolyte layer, with a gel electrolyte layer transfer sheet. The gel electrolyte layer transfer sheet is prepared, for example, by coating a support sheet with a slurry obtained by dispersing the material that constitutes the gel electrolyte layerin a solvent and then drying the slurry. The pressing pressure may be any pressure that can integrate the electrolyte layer.

Note that the machine used to manufacture the solid-state batterywithout the intermediate layermay be, but is not limited to, a roll press machine or flat plate press machine.

The solid-state battery may be, but is not limited to, a solid-state lithium metal battery. The following will describe the case where the solid-state batteryis a solid-state lithium metal battery.

The negative electrode composite layeris a lithium metal layer. The negative electrode charge collectormay be, but is not limited to, a copper foil, for example.

The positive electrode composite layercontains a positive electrode active material and may further contain a solid-state electrolyte, a conductivity aid, a binding agent, and the like. The positive electrode active material may be any material that can absorb and release lithium ions, for example, lithium nickel cobalt manganese composite oxide. The solid-state electrolyte may be any material that has lithium-ion conductivity, for example, an oxide-based electrolyte or sulfide-based electrolyte. The conductivity aid may be any material that has electron conductivity, for example, carbon black. The binding agent may be any material that can improve binding properties, for example, styrene butadiene rubber.

The positive electrode charge collectormay be, but is not limited to, an aluminum foil.

The first solid-state electrolyte layerand the second solid-state electrolyte layercontain a solid-state electrolyte. The solid-state electrolyte may be any material that has lithium-ion conductivity, for example, an inorganic solid-state electrolyte, such as an oxide-based electrolyte or sulfide-based electrolyte. Note that the first solid-state electrolyte layerand the second solid-state electrolyte layermay be composed of either the same solid-state electrolyte or different solid-state electrolytes.

The gel electrolyte layercontains a matrix resin, an electrolyte, and a solvent. The matrix resin may be any material that can gel and integrate the electrolyte layer, for example, polyethylene oxide. The electrolyte may be any material that has lithium-ion conductivity, for example, a lithium salt. The solvent may be any material that can dissolve the electrolyte, for example, a carbonate solvent.

The intermediate layercontains a metal that can be alloyed with lithium and amorphous carbon and may further contain a binding agent and the like. The metal that can be alloyed with lithium and amorphous carbon are preferably nanoparticles. Examples of the metal that can be alloyed with lithium include tin (Sn), silicon (Si), zinc (Zn), magnesium (Mg), gold (Au), platinum (Pt), palladium (Pd), silver (Ag), aluminum (Al), bismuth (Bi), and antimony (Sb). Examples of the amorphous carbon include carbon blacks such as acetylene black, furnace black, and Ketjen black, coke, and activated carbon. The amorphous carbon may be graphitizable carbon (soft carbon), non-graphitizable carbon (hard carbon), CNTs (carbon nanotubes), fullerenes, or graphene. The binding agent may be any agent that can improve binding properties, for example, polyvinylidene fluoride (PVDF).

The intermediate layer, which has the function of depositing lithium metal uniformly, stabilizes the interface between the intermediate layerand the first solid-state electrolyte layer. If the solid-state batteryhas the intermediate layer, the solid-state batterymay be an anode-free battery in which the lithium metal layer as a negative electrode composite layeris not formed at the initial charge. In an anode-free battery, a lithium metal layer as a negative electrode composite layeris formed after the first charging and discharging.

The thickness of the intermediate layermay be, but is not limited to, greater than or equal to 4 μm and less than or equal to 10 μm.

The material that constitutes the insulating framemay be, but is not limited to, an insulating oxide, such as alumina, a resin, such as polyvinylidene fluoride (PVDF), or a rubber, such as styrene butadiene rubber (SBR).

Although the embodiment of the present invention has been described above, the present invention is not limited to the above-mentioned embodiment, and the above-mentioned embodiment may be modified as appropriate without departing from the scope of the present invention. For example, the solid-state batterymay further include an exterior package (e.g., a laminating film) that encloses the electrode laminate.